\documentclass{article}
\usepackage{amssymb,amsmath,amscd,concmath}
\pagestyle{empty}
\begin{document}
\begin{equation*}
y = \left\{ \begin{array}{ll}
P(X = 2) = 0& \textrm{if Cat=0}\\
P(X \geq 1 \geq P(X=0) \geq 0) &\textrm{else}\\
\end{array} \right. \iff \# tails=3
\end{equation*}
\end{document}
